The benz[c,d]indole ring system (I) has been known since 1949. ##STR1## For example Uhle et al. J. Am. Chem. Soc., 71, 1611 (1949); ibid, 73, 2402 (1951); Grob et al. Helv. Chim. Acta., 33, 1796, 1955 (1950), 35, 2095 (1952), 36, 839 (1953) and Stoll et al. ibid, 33, 2254, 2257 (1950); 35, 148 (1952), prepared, among other compounds, a 5-keto-1,3,4,5-tetrahydrobenz[c,d]indole plus the corresponding 4-amino and 4-acetylamino derivatives. A useful starting material for the synthesis of these compounds was a 1-benzoyl-1,2,2a,3,4,5-hexahydro derivative, II. ##STR2## formed by the Friedel-Crafts ring closure of 1-benzoyl-2(3-indolinyl)propionylchloride. Kornfeld et al., J.A.C.S., 78, 3087 (1956) also prepared this compound and converted it, via a series of intermediates, to the 4-amino-5-keto derivative which was, in itself, a key intermediate in the first total synthesis of lysergic acid. In this synthetic procedure, a fourth ring (an N-methyl piperidine ring) was grafted onto an appropriately substituted tricyclic 1,2,2a,3,4,5-hexahydrobenz[c,d]indole. Stoll et al. Helv. Chim. Acta, 35, 148 (1952) also prepared (.+-.)-4-dimethylamino-1,3,4,5-tetrahydrobenz[c,d]indole. Bach and Kornfeld, U.S. Pat. No. 4,110,339, prepared the corresponding 4-(di-n-propyl)amino compound. Ledelec et al, U.S. Pat. No. 4,447,438 discloses 4-piperidyl-substituted-1H-indole having dopaminergic properties.
Certain naturally occurring alkaloids, agroclavine and elymoclavine, have been converted by Cassady et al. J. Med. Chem., 17, 300 (1974) to N-methyldioxychanoclavine, N-methylchanoclavine, and chanoclavine, all 4,5-disubstituted tetrahydrobenz[c,d]indoles (III). ##STR3## wherein X is H or OH and R.sup.1 is CH.sub.3 or H. Compounds according to III were without significant prolactin inhibiting activity, unlike the Bach-Kornfeld (.+-.)-4-(di-n-propyl)amino-1,3,4,5-tetrahydrobenz[c,d]indole, which was found to be a selective dopamine agonist as shown by its action in inhibiting dopamine uptake in bovine striatal membrane in vitro. The corresponding 4-(dimethyl)amino derivative of Stoll et al. (loc. cit.) was used only as an intermediate. The 4-aminotetrahydrobenz[c,d]indoles and related derivatives are weak serotonin antagonists with one exception, the 4-acetylamino-5-oxo derivative--see Harris and Uhle, J. Pharm. & Exper. Therap., 128, 358 (1960).